This invention relates generally to a check valve, and more particularly to a manually operable swing check valve intended for use in a sanitary sewer system which can be easily converted in the field from right to left hand operation or vice versa. A wide variety of check valves are available to permit fluid to flow in one direction in a conduit to prevent it from flowing in the other. When used in sanitary sewer systems such valves must exhibit a high degree of reliability and a resistance to clogging and corrosion. They should be relatively compact and ideally should be usable in vertical as well as horizontal conduits. Also, they should be relatively inexpensive to manufacture and easy to repair.
If the check valve is to be used as a sump valve in a sanitary sewer lift station additional requirements may be imposed. In many conventional lift stations, a check valve is positioned immediately downstream of each sump pump to permit flow to pass in the downstream direction, but to prevent any reverse flow into the pump. In such systems it is necessary that the pump impellers be cleaned periodically and highly desirable that the cleaning can be done without removing the pumps from the lift station. The easiest way to accomplish this is to block the discharge side of each pump while it is running and allow the pressurized fluid on the discharge side to clean the impeller. The check valves normally employed cannot be used for this purpose because they are designed to block flow only in the direction of the pumps. A conventional shutoff valve can be added to the discharge line, but this solution will increase the cost of the system and will require the operator to stock two different valves for repair purposes. Accordingly, it would be desirable to provide for a check valve which could be selectively used to block flow in either direction.
For reliability and economy, any such check valve should be manually operable. The limited accessability of the pumps and check valves in many lift stations requires that both valves be operable from the same side, while the design of the discharge system requires that the valves be mounted in opposite directions. To satisfy these requirements, right and left hand models of the same valve ordinarily would have to be manufactured, and the two different models would have to be stocked for repair purposes.
In an effort to provide an improved swing check valve the inventor herein developed the valve described in U.S. Pat. No. 3,612,097, which was issued on Oct. 12, 1971. The valve disclosed in that patent represents a definite advance in the state of the art and has achieved significant commercial success. The valve is not designed for manual operation, however. Also, experience with the valve has indicated that certain modifications and improvements are desirable. Under some flow conditions the valve tended to spin when open, resulting in an undesirable amount of wear on the rivet used to join the valve and arm. Also the receding valve seat protruded radially inward of the inner wall of the flow passageway to facilitate removal, but tended to cause debris to collect upstream of the seat and interfere with seating. In an effort to provide for a manually operable swing check valve which could be easily converted for use in either position in a lift station and to further improve the patented valve the present invention was made.